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Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(5), p.133 - 137, 2022/05
The effect of the corrosion inhibitor on the corrosion of steel under a thin solution layer was investigated. As a result of forming a thin solution layer with a thickness of 1.0-0.2 mm on the specimen, adding a mixed solution of sodium molybdate and aluminum lactate as a corrosion inhibitor, and performing electrochemical measurement, the corrosion inhibitor suppresses the anodic reaction. And in the thin solution layer, it was suggested that the morphology of the protective layer structure by the corrosion inhibitor changed according to the amount of liquid as compared with the bulk immersion.
Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(4), p.121 - 125, 2022/04
The effect of solution layer thickness on the atmospheric corrosion of carbon steel was investigated using novel devices fabricated by a 3D printer. These novel devices allowed us to control the solution layer thickness precisely. Potentiodynamic polarization measurements were performed under thickness-controlled solution layer, and oxygen diffusion limiting current density (
) and anodic current density (
) were measured. As the solution layer become thinner, increased and decreased. This result indicates that corrosion accelerates when the solution layer becomes thinner. The diffusion coefficient of oxygen was calculated as 3.20
10
cm
s
from the relationship between and solution layer thickness, and the critical diffusion thickness was estimated to be 0.87 mm.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
Tetsu To Hagane, 107(12), p.998 - 1003, 2021/12
In order to clarify the effect of environmental factors on the amount of atmospheric corrosion of steel, novel model for predicting the reduction of atmospheric corrosion considering relative humidity and rain falls was developed. We conducted a one-year calculation simulation of atmospheric corrosion in Miyakojima City, Choshi City, and Tsukuba City using the developed model. Corrosion weight loss by the simulation could reproduce the measured value well. Corrosion weight loss at each point was greatly affected by the amount of flying sea salt, relative humidity, and rain falls.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
Bosei Kanri, 65(10), p.365 - 370, 2021/10
We have developed a new atmospheric simulation model considering important environmental factors such as airborne sea salt, temperature, relative humidity, and rainfall. The developed model was verified by comparing predicted values by the simulation and measured data for the weight loss by atmospheric corrosion. In addition, atmospheric corrosion simulations under open and sheltered exposure condition were conducted, and it was confirmed that the air corrosion weight loss was strongly suppressed by the surface cleaning effect due to rainfall.
Otani, Kyohei; Sakairi, Masatoshi*
Materials Transactions, 62(6), p.815 - 820, 2021/06
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The synergistic effects of metal cations in a solution on the ability of sodium gluconate to inhibit the corrosion of mild steel were investigated quantitatively focus on the parameter Y, which represents the "corrosion inhibitory effect of cations" by immersion and electrochemical tests. The results of the investigations showed that the inhibition ability of gluconates improved with increasing Y value of the metal cations in model freshwater. The electrochemical and surface analyses indicated that gluconate ligands and large-Y metal cations formed a protective film with few defects on the mild steel.
Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki; Sakairi, Masatoshi*; Togashi, Yusuke*; Baba, Kazuhiko*; Takagi, Shusaku*
ISIJ International, 61(4), p.1085 - 1090, 2021/04
In order to clarify the effect of metal cations (Zn
, Mg, Na
) in aqueous solution on hydrogen permeation into iron, the amount of hydrogen permeation from iron surface was measured by electrochemical tests with a laser ablation. Moreover, in order to obtain the basic mechanism of hydrogen permeation with metal cation, first-principles calculations were used to acquire the adsorption potential of the metal cation and the electronic state around iron surface. By Zn in solution, anodic reaction on ablated surface by laser irradiation was suppressed. Also, by quantum analysis Zn atoms were chemically bonded stronger than Na and Mg atoms to iron surface. It was suggested that the dissolution reaction of iron was suppressed by the formation of the Zn layer, and that lead suppression of hydrogen permeation into iron.
concentrationOtani, Kyohei; Islam, M. S.*; Sakairi, Masatoshi*; Kaneko, Akira*
Surface and Interface Analysis, 51(12), p.1207 - 1213, 2019/12
Times Cited Count：0 Percentile：0(Chemistry, Physical)The corrosion morphology and composition of corrosion products of A3003 formed in model fresh water with different Zn concentrations were investigated by immersion tests combined with surface observations and analysis using an auger electron spectroscope (AES). The cross-sectional AES observations showed that the thickness of the corrosion product layer formed on A3003 decreases with increases in the Zn concentration of the model fresh water. A cross-sectional AES point analysis suggested that the corrosion products formed on the A3003 in the Zn containing model fresh water (Zn 
0.1 mM) have a multi-layer structure, and that the inner of Zn-rich layer would have high corrosion protective properties.
Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*
ISIJ International, 58(9), p.1616 - 1622, 2018/09
Times Cited Count：3 Percentile：28.45(Metallurgy & Metallurgical Engineering)To elucidate the role of Zn on corrosion of coated steel, the effects of metal cations on the corrosion of carbon steel in the concentrated Cl
aqueous solutions were studied by immersion tests, surface analysis and electrochemical tests. Among the examined metal cations, Zn showed the significant effect on corrosion inhibition of carbon steel in the Cl aqueous solution at high concentration. XPS analysis results elucidated that Zn can remain on the steel surface after immersed in the solutions with Zn. EIS measurements showed higher impedance in the solution with Zn than other solutions, and the results suggested that Zn reduced the defect points in the thin oxide film by forming a metal cation layer. Based on the experimental results, Zn may form a layer on the oxide film that protects the Cl attack in the solution. The findings demonstrated that the formation of Zn layer on the oxide film is one of the main reason for showing high and longtime corrosion resistance of Zn coated steel substrate.
aqueous solutionIslam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*
Corrosion Science, 140, p.8 - 17, 2018/08
Times Cited Count：7 Percentile：49.28(Materials Science, Multidisciplinary)The corrosion characteristics of SUS304 exposed to 0.5M Cl aqueous solution containing different metal cations were studied with immersion tests, surface analysis and electrochemical tests. The mechanism of corrosion with metal cations was clarified by the XPS analysis results together with the hard and soft acid and base (HSAB) concept and the passive films structure. It is supposed that metal cations with large hardness make a layer by chemical bonding with the passive films. The passive films are protected by the metal cation layer from Cl attack, and consequently corrosion reactions are inhibited.
Otani, Kyohei; Sakairi, Masatoshi*; Kaneko, Akira*
no journal, ,
The effects of metal cations on corrosion of A3003 aluminum alloy in model fresh water were investigated by electrochemical techniques and immersion tests. The electrochemical and immersion results showed that hardness of metal cation, X is not suitable as a corrosion indicator of A3003. A novel corrosion indicator is proposed, and it is shown that the novel indicator can estimate the corrosion rate of A3003 in fresh water.
Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*
no journal, ,
In the previous study, it was founded that Zn significantly inhibited the corrosion of mild steel in Cl aqueous solution at room temperature. It is still not fully elucidated the corrosion inhibition ability of Zn concentration on the steel in Cl aqueous solutions. In the present study, the effects of Zn concentration on the corrosion inhibition of mild steel were investigated by immersion tests. From the immersion tests, it was found that mass change of specimen closely related to the Zn concentration in the solutions. SEM images showed that the numbers of pits are decreasing with increasing the Zn concentration. XPS and AES results showed that Zn existed as hydroxides by forming a layer with the surface film and the coverage of the layer is increased with increase in Zn concentration.
Sakairi, Masatoshi*; Otani, Kyohei; Islam, M. S.*
no journal, ,
Previous studies showed that zinc ion shows higher corrosion resistant property on corrosion of metals in aqueous environment. It is, however, not fully elucidate role of zinc ions on corrosion inhibition of metals in aqueous environments. In this study, the effects of zinc ion on corrosion behavior of aluminum alloy and steels in aqueous environments. From electrochemical and surface analysis results, zinc ion may forms a very effective shielding film which can block the electrochemical reactions, consequently lowers the corrosion rate.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
no journal, ,
From the viewpoint of environmental and energy problems, research on atmospheric corrosion of steel materials is one of the important themes. In this study, we focused on the liquid film thickness, which is one of the environmental factors greatly related to the amount of corrosion, and constructed and simulated a corrosion prediction model using the amount of adsorbed salt and relative humidity as parameters. The developed model made it possible to express changes in corrosion rate due to changes in relative humidity day and night. In addition, there were times when the corrosion rate changed drastically during the day. Analysis of the simulation data suggested that this might be a change in the liquid film thickness due to the deliquescent of the contained salt.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
no journal, ,
Large structures such as bridges and nuclear facilities in the sea shore area are exposed to a severe corrosive environment by airborne sea salt. From the viewpoint of ensuring facility safety and environmental and energy issues, it is one of the important themes to elucidate the mechanism of atmospheric corrosion of steel materials, which are the main materials of large structures. In the study, we modified existing model in which precipitation and humidity were considered as influential factors for atmospheric corrosion, and developed a novel model for predicting atmospheric corrosion loss with additional consideration of temperature. The developed model corrected the excessive prediction of corrosion amount by the existing model, and enabled more precise prediction of atmospheric corrosion weight loss.
